Printing mechanism with overdrive for the printing cylinder and inking rollers

ABSTRACT

A printing mechanism for a printing and punching machine of the type having stepwise advance of a web of paper to be printed or for sheet printing presses includes a printing cylinder which is adapted to be constantly rotated in the same rotary direction as it is transversely reciprocated back and forth across an impression plate. The drive for the printing cylinder comprises a motor driven eccentric crank shaft drive means, and mounted on the shaft of the printing cylinder is an overdrive mechanism for rotating the printing cylinder at a reduced speed as the cylinder reaches the end positions of its reciprocating stroke in order to ensure the constant rotation of the printing cylinder and its associated inking mechanism in order to obtain the uniform transfer of ink from the inking rollers to the printing plate.

United States Patent 1191 Ebneter July 23, 1974 [75] Inventor: Markus Ebneter, St. Gallen,

Switzerland [73] Assignee: Firma Ferd. Ruesch Maschinenfabrik, St. Gallen, Switzerland [22] Filed: July 14, 1972 [21] Appl. No.2 271,871

30 Foreign Application Priority Data Apr. 21, 1972 Germany 2219534 [52] US. Cl 101/21 2,'101/260, 101/354 [51] Int.'Cl. 1341f 3/02, B41f 5/00 Field of Search 101/260, 214, 215, 252, 101/266, 269, 277, 282, 253, 275, 272, 273,- 274, 264, 55, 133, 146, 158, 173, 186, 212,354

[56] References Cited UNITED STATES PATENTS PRINTING MECHANISM WITH OVERDRIVE FOR THEPRINTING CYLINDER AND INKING ROLLERS 9/1872 Potter Jr. 101/282 4/l935 Nixon l0l/2l2 Primary Examiner-Robert E. Pulfrey Assistant Examiner-Paul J. Hirsch [5 7 ABSTRACT A printing mechanism for a printing and punching machine of the type having stepwise advance of a web of paper to be printed or for sheet printing presses includes a printing cylinder which is adapted to be constantly rotated in the same rotary direction as it is transversely reciprocated back and forth across an impr'ession plate. The drive for the printing cylinder comprises a motor driven eccentric crankshaft drive means, and mounted on the shaft of the printing cylinder is an overdrive mechanism for rotating the printing cylinder at a reduced speed as the cylinder reaches the end positions of its reciprocating stroke in order to ensure the constant rotation of the printing cylinder and its associated inking mechanism in order to obtain A the uniform transfer of ink from the inking rollers to the printing plate:

2 Claims, 6 Drawing Figures 1 PRINTING MECHANISM WITH OVERDRIVE FOR THE PRINTING CYLINDER AND INKING ROLLERS The present invention relates to a transfer printing mechanism for printing and punching machines of the type having stepwise feed, wherein the printing cylinder is provided with a printing plate over a part of its circumference, and is rolled against a flat impression plate during the stoppage of a web of paper or sheet and, after the rolling, the printing cylinder returns to the starting position while the next feed operation occurs. During its backward and forward movement the printing cylinder is turned continuously in the same di rection by means of two racks which are alternatively engaged via pawls, and during the return movement of the crank drive the printing plate is inked by an inking mechanism which is arranged above the printing cylinder. The inking mechanism is driven from a crank drive via the printing cylinder.

Conventional transfer printing mechanisms of the type disclosed in German Pat.No. 482 999 and Danish Pat. No. 50,966, wherein the drive of the transfer printing mechanism simultaneously drives the inking mechanism, have the disadvantage that the speed of the backward and forward motion and thus the rotary movement of the printing cylinder rises from the corresponding end position from and drops towards the end back to 0 and therefore describes a sinusoidal curve. As a result, the inking rollers also come to a standstill, which leadsto a nonuniform transfer of ink from the inking rollers to the plate and thus to the formation of transverse shadings of the printing.

it has furthermore been found disadvantageous in conventional printing mechanisms that after the stoppage, the pawls of the transfer printing mechanism suddenly drop into the associated ratchet when the backward and forward movement starts again, as a result of which they are subject to strong wear which impairs the precision of register.

Accordingly, the object of the present invention is to overcome the shortcomings of the prior art devices, and to provide a new and improved transfer printing mechanism in which the printing cylinder and, via it the associated inking I mechanism, are continued to be driven during a stoppage of the reciprocation and of the rotary movement of the cylinder and of the inking mechanism driven by it, which is caused by the crank drive.

In order to avoid the stoppage of the inking mechanism it has already been proposed to drive it by a spetate the cylinder via a free wheel with linear speed as soon as the speed produced by the crank drive drops below said linear speed and which goes out of operation due to the free wheel when the speed (which rises and falls in the form of a sinusoidal curve) exceeds the linear speed. The printing cylinder is developed in such a fashion that the printing plate extends lengthwise over half the circumference of the cylinder less the path which the rotary movement moves over during drive by the overdrive.

The stroke of the crank drive is preferably shortened as compared with an arrangement without overdrive by the distance which is required to move over the rotary movement of the printing cylinder effected by the overdrive.

The overdrive is preferably applied via a worm to a M drive gear of the printing cylinder which is connected cial drive during the stoppage of the printing cylinder,

for instance by a slowly rotating electric motor. This inking mechanism drive must, however, operate in synchronism with the increasing and decreasing speed of the movement of the printing cylinder, which is expensive from the standpoint of control technique. p

The solution of the problem is found in the transfer printing mechanism of the present invention which has the inking mechanism driven by the printing cylinder and which is reciprocated from the main drive of the machine via an eccentric and a crank rod arranged on same, whereby the cylinder, which is rolled with gears along two fixed racks into which pawls alternately engage, is turned constantly in the same direction and in association with which there is provided on the machine main drive an overdrive which continues to roby two gears with the main drive shaft of the machine by which the eccentric of the crank drive is also driven. Between the drive shaft of the overdrive and the printing cylinder there is arranged an overriding clutch which disconnects the drive from the printing cylinder when the overdrive is driven by the crank drive via the worm with a speed which is higher than the uniformly constant speed of the overdrive.

By the arrangement in accordance with the invention the result is obtained that the inking mechanism which is driven by the rotation of the printing mechanism is continued to be driven with reduced but constant speed shortly before and after the printing cylinder has reached the end position of the linear movement and of the speed dropping to O and rising from 0. In this way there is obtained a constantly uniform distribution of ink and transfer of ink to the printing plate.

The arrangement in accordance with the invention furthermore has the advantage that the gears of the printing cylinder and the pawls are assured very gently treatment since, upon the change of the linear movement of the cylinder, the pawls do not fall suddenly into position but rather catch up with the rotation of the gears with increasing speed of the crank drive and slowly slide into the teeth. The accuracy of register is retained even after a long period of operation in view of the lack of wear. Rapid forward movement of the sprocket gear by sudden engagement of the pawls is avoided.

Since the crank drive need rotate only 360 less the rotation effected by the overdrive, the stroke of the crank can be shortened. In this way there are obtained more favorable conditions of momentum which permit a lighter construction of the printing mechanism and of the drives.

For further explanation of the invention, reference is made to the accompanying drawings in which:

FIG. 1 is a diagram of a known prior art transfer printing mechanism with crank drive;

FIG. 2 is a diagram of the transfer printing mechanism of the present invention;

FIG. 3 is a diagram of the subject printing mechanism directly before the start of the printing process;

FIG. 4 is a diagram of the subject printing mechanism directly before the end of the printing process;

FIG. 5 is a diagram, partially in section, showing the drive of the subject printing cylinder;

FIG. 6 is a speed diagram.

As can be noted from FIG. 1, in the prior art transfer printing mechanism, the printing cylinder is recipro- 3 cated by a crank rod over the distance designated by the letter A, namely twice the distance from the point of support of the crank rod on the eccentric to its center. As a result of the crank drive, the speed of the linear, and thus also of the rotary movement of the printing cylinder increases and decreases from to 0 in accordance with the sinusoidal curve shown in FIG. 6.

As shown in FIG. 2, in the apparatus of the present invention, the rotation is produced for thesame distance as in FIG. 1, namely half a revolution of the cylinder (i.e., 180) while the linear movement of the printing cylinder covers only the distance A-x, namely the distance less the linear movement required by the rotary movement effected by the overdrive. Accordingly there is obtained a speed curve shown in FIG. 6 which is linear at the beginning and the end of the stroke, and

- sinusoidal over most of its length, and in connection with which the linear speed portion is caused by the overdrive and the sinusoidal speed portion by the crank drive.

Referring to FIGS. 3 5, the transfer printing mechanism of the subject invention consists of a printing cylinder 1 having a printing plate 2 extending over a part of its circumference, an eccentric wheel 3, and a crank rod 4, along with an impression plate (not shown) on which a web of paper or a sheet is placed for printing. On the shaft 15 (seeFIG. of the printing cylinder 1 there is arranged a ratchet wheel 16 keyed thereon, as

- well as gears 17 and 18 for racks 5 and 7, respectively.

The gears 17 and 18 are rotatably mounted on shaft 15. On thegears 17,, 18 there are provided pawls 19, 20, respectively. On the shaft there is also provided a gear 21 having overriding clutch24. The gear 21 is in engagement with the worm 22 which is slidably mounted on and guided in grooves on the shaft 23 of I the overdrive. In turn, shaft 23 is connected via gear 25 (see FIGS. 3 and 4) with the gear 26 of the main drive shaft 27 which is driven by the motor M. The drive shaft 27 drives the eccentric wheel 3 via gearing 28. As

shown in FIG. 5, pawl 20 is in connection with drive wheel 16, while pawl 19 is out of operation. It is noted that alternatively one pawl is in operation while the other pawl is not in contact with the wheel 16. The wheel 16 is provided with recesses into which fall alternatively the pawls l9 and 20.

Above the printing cylinder 1 there is arranged thev inkingmechanism whichconsists of a stationary ink fountain 8,' a doctor roller 9 and a vibrator roller 10 by which the ink is transferred from the fountain 8 to the distributing cylinder 11 which permits transverse distribution. The'transfer roller 12 then applies the ink to the spreading rollers 13 and from the latter via the inking rollers 14 to the printing plate 2.

Upon the forward advance of the printing cylinder 1 by the connecting rod 4 on the eccentric wheel 3, the

gear 17 which is in engagement with the rack 5 turns and, by means of the pawl 19, drives the ratchet wheel 16. In this way the printing cylinder 1 is rotated and the printing plate 2 rolled over the web of paper.

Upon the return travel the gear 18 which is continuously in engagement with the rack 7 turns the sprocket wheel 16 via the pawl 20 so that even upon the rearward movement, after the printing process, the printing cylinder 1 is turned in the same direction of rotation as upon the forward motion.

During the forward motion the printing plate 2rolls over the stationary web of paper or sheet. The inking mechanism moves, in combination with the rack 7, in the same direction. After termination of the printing operation, the web of paper is pulled forward a further step below the rearward moving printing cylinder. No contact takes place between the printing cylinder and the web of paper since the protruding printing plate 2 of the printing cylinder 1 is located outside the vertical line to the web of paper. Upon the return movement, the printing plate 2 is again inked by the inking rollers 14.

In order to prevent complete stoppage of the rotation of the printing cylinder 1 when the corresponding end position of the linear movement is reached, the printing cylinder 1, shortly before completion of the printing process and the reduction in speed of the linear and rotary motion taking place thereby, is turned further via the gear 21 by the worm 22 of the overdrive with a reduced but constant speed, as a result of which the rollers of the inking mechanism are also uniformly'turned further.

.What is claimed is:

1. A transfer printing mechanism for a printing and punching machine having step-wise advance of a web of paper to be printed or for sheet printing presses, comprising:

a printing cylinder mounted on a shaft for rotary and reciprocating movement relative to a stationary impression plate;

an inking mechanism disposed above said printing cylinder means driving said inking mechanism by said printing cylinder; and

means for driving said printing cylinder in a rotary and a reciprocating manner relative to said impression plate, said driving means including:

a motor, an eccentric drivingly connected to said motor, a crank connecting said eccentric to said printing cylinder for reciprocatingv said printing cylinder back and forth across said impression plate;

means including gears mounted on the shaft of said printing cylinder for driving the latter in the same rotary direction during its reciprocation back and forth across said impression plate, said gears being driven by drive members on the machine frame; and

an overdrive mechanism for rotating said printing cylinder separate and apart from said gear driving means, including an overriding clutch mounted on said shaft, said clutch being concylinder less the angular distance that the cylinder ro-- tates during operation of the overdrive mechanism. =l= 

1. A transfer printing mechanism for a printing and punching machine having step-wise advance of a web of paper to be printed or for sheet printing presses, comprising: a printing cylinder mounted on a shaft for rotary and reciprocating movement relative to a stationary impression plate; an inking mechanism disposed above said printing cylinder means driving said inking mechanism by said printing cylinder; and means for driving said printing cylinder in a rotary and a reciprocating manner relative to said impression plate, said driving means including: a motor, an eccentric drivingly connected to said motor, a crank connecting said eccentric to said printing cylinder for reciprocating said printing cylinder back and forth across said impression plate; means including gears mounted on the shaft of said printing cylinder for driving the latter in the same rotary direction during its reciprocation back and forth across said impression plate, said gears being driven by drive members on the machine frame; and an overdrive mechanism for rotating said printing cylinder separate and apart from said gear driving means, including an overriding clutch mounted on said shaft, said clutch being connected to said motor so that said overdrive mechanism is operative to rotate the printing cylinder at a speed less than the maximum speed of the speed of rotation produced by the eccentric crank means and thereby insure the constant rotation of the inking means throughout the entire reciprocating stroke of said printing cylinder.
 2. A transfer printing mechanism as in claim 1 wherein the printing cylinder includes a printing plate which extends over one-half the circumference of the cylinder less the angular distance that the cylinder rotates during operation of the overdrive mechanism. 